Hot melt anti-surge dispensing system

Abstract

The invention pertains to a system for dispensing highly viscous materials, such as hot melt adhesives, wherein flow surges are eliminated. The material is pumped by an expansible chamber motor operated by compressed air and flow through a dispensing nozzle is controlled by a valve. Air pressure regulators provide a low pressure on the material when no dispensing is occurring, and a higher pressure is imposed upon the air motor during dispensing. Selectivity between air pressures is regulated by an electric switch simultaneously operated with the dispensing nozzle wherein the higher dispensing pressure is imposed on the pump motor only after the nozzle has been opened, thereby preventing material flow surges. If dispensing occurs through a plurality of nozzles communicating with a common pump additional air pressure regulators are provided to increase the pump flow proportional to the amount of material being dispensed to provide uniform dispensing characteristics from each of the dispensing nozzles.

I claim: 
     
       1. An anti-surge dispensing system for viscous materials wherein the system includes a pump for the material operated by an expansible chamber air motor powered by a compressed air source and a valved dispensing nozzle in communication with the pump, the improvement comprising air pressure control means interposed between the air motor and compressed air source controlling the air pressure supplied to the air motor in accordance with the condition of the valve of the dispensing nozzle, said air pressure control means including a first air pressure regulator having a low air pressure output, a second air pressure regulator having an air pressure output higher than that of said first regulator, electrically operated valve means communicating with said regulators and the air motor having a first position supplying low pressure air to the air motor and a second position supplying higher pressure air to the air motor, and an electric switch simultaneouly operated with the valve of the dispensing nozzle controlling the position of said valve means whereby a low air pressure is supplied to the air motor when the dispensing nozzle valve is closed and a higher air pressure is supplied to the air motor when the dispensing nozzle valve is opened. 
     
     
       2. In an anti-surge dispensing system as in claim 1, a hand held dispensing gun, the valved dispensing nozzle being defined on said dispensing gun, said gun including a manual valve operating trigger, and said electric switch being operated by said trigger. 
     
     
       3. In an anti-surge dispensing system as in claim 1, wherein the dispensing system includes a second valved dispensing nozzle in communication with the pump, said air pressure control means including a third air pressure regulator having a high pressure output of a higher pressure than that of said second regulator, said third regulator communicating with said electrically operated valve means, and a second electric switch simultaneously operated with the valve of the second dispensing nozzle electrically connected to said valve means whereby operation of both electric switches during simultaneous dispensing through both nozzles operates said electrically operated valve means to supply high pressure compressed air from said regulator to the air motor. 
     
     
       4. An anti-surge dispensing system for viscous materials comprising, in combination, a viscous material expansible chamber pump having a material inlet and a pumped material outlet, an expansible chamber air motor operatively connected to said pump and having a compressed air inlet, a source of compressed air, air pressure control means interposed between said source of compressed air and said air motor, said control means including a first air pressure regulator having a low air pressure output, a second air pressure regulator having an air pressure output higher than that of said first regulator, electrically operated valve means communicating with said regulators and communicating with said air motor inlet controlling the supply of compressed air to said air motor having a first position supplying low pressure air to said air motor and a second position supplying high pressure air to said air motor, a first valved dispensing nozzle communicating with said pump outlet selectively dispensing pumped material, and a first electric switch simultaneously operated with the valve of said first dispensing nozzle controlling the position of said valve means whereby a low air pressure is supplied to said air motor when the valve of said dispensing nozzle is closed and a higher air pressure is supplied to said air motor when the dispensing nozzle valve is open. 
     
     
       5. In an anti-surge dispensing system as in claim 4, said valved dispensing nozzle comprising a hand held gun having a manually operated trigger, said electric switch and the nozzle valve being operated by said trigger. 
     
     
       6. In an anti-surge dispensing system as in claim 4, said air pressure control means including a third air pressure regulator having an air pressure outlet higher than that of said second regulator, said third regulator output communicating with said electrically operated valve means, a second valved dispensing nozzle communicating with said pump outlet selectively dispensing pumped material, a second electric switch simultaneously operated with the valve of said second dispensing nozzle controlling the position of said valve means, said valve means including a third position supplying high pressure air from said third regulator to said air motor, said switches being connected in parallel to said valve means to position said valve means to said second position if either switch is operated during dispensing from a single nozzle, and said switches being connected in series to said valve means to position said valve means to said third position when both switches are operated during simultaneous dispensing from said first and second nozzles. 
     
     
       7. In an anti-surge dispensing system as in claim 6, said electrically operated valve means comprises first and second solenoid operated valves, said first valve being connected to said first and second regulators, said second valve being connected to said third regulator, and said switches being connected in parallel to said first valve and being connected in series to said second valve.